1. Field of the Invention
The present invention relates to a method of preparing a carrier to separate nucleic acids, a carrier and micro channel to separate nucleic acids, and a method and apparatus of separating nucleic acids. More particularly, the present invention relates to a method of preparing a cation-exchangeable porous carrier to separate nucleic acids.
2. Description of the Related Art
Recent years have seen a remarkable development in bioassay technologies applicable to gene mutation analysis, single nucleotide polymorphism (SNPs) analysis, gene expression frequency analysis, and gene network elucidation. Such technologies employ integrated substrates called DNA (Deoxyribonucleic Acid) chips or DNA microarrays (which will be collectively referred to as DNA chips hereinafter).
The sensor chip technology that employs DNA chips and protein chips (with proteins integrated thereon) is designed to separate and detect a target substance in a sample and determine its content with the help of specific interactions between a target substance and a detecting substance.
There has recently been proposed a new technology that employs a fluid channel or capillary for interactions between a target substance and a detecting substance. The interaction between substances is applied to a new technology that causes the hybridization reaction of nucleic acids to take place in a fluid channel or capillary. For example, Japanese Patent Laid-open No. 2005-130795 (hereinafter referred to as Patent Document 1) discloses an apparatus for analysis of polynucleotide which includes a section for amplification of polynucleotide and a section for hybridization which has a porous layer to which is fixed a detecting oligonucleotide, with the sections being connected to each other through a fluid channel. Also, Japanese Patent Laid-open No. 2004-121226 (hereinafter referred to as Patent Document 2) discloses a method of analyzing polynucleotide by allowing hybridization to take place between a probe compound (fixed to the inside of a capillary fluid channel) and a target polynucleotide.
The interaction between substances that takes place in a thin fluid channel such as capillary poses a problem with a significant pressure rise in the channel which results from flowing sample solutions. In the case where a nucleic acid chain is the target substance, it forms a hybrid in the thin fluid channel to reduce the substantial volume of the channel and increases the pressure in the channel. Moreover, nucleic acid chains other than target nucleic acid chains may adsorb nonspecifically to the inside of the channel to clog the channel and increase the pressure in the channel.
The increased pressure in the channel causes solutions to leak out from joints and any other weak parts. Loss of solutions due to leakage reduces the amount and concentration of reaction substances, which would prevent the expected interactions between substances. Moreover, leakage could endanger safety if the sample solution contains hazardous materials.
To cope with the foregoing situation, the present inventors have proposed a micro fluid channel which is free from clogging and pressure increase, as disclosed in Japanese Patent Laid-open No. 2007-309900 (hereinafter referred to as Patent Document 3). This micro fluid is made up of two sections. The first one is filled with beads for hybrid formation. The second one is placed in the downstream region of the first one (or the hybrid forming section) so that it permits solutions to flow rapidly.